1. Field of the Invention
The present invention relates to communication devices and specifically fiber-optic cable devices.
2. Description of the Prior Art
Fiber-optic cables are commonly used in modern communication systems. When a fiber-optic cable is deployed in a network, various network drawings and architectural drawings are produced to depict the network. As such, when operations need to be performed on the fiber-optic cable, a technician may use the network drawings.
A conventional fiber-optic cable includes several fiber strands surrounded by protective layers. Each fiber strand consists of a glass-like core. Communication is accomplished in a fiber-optic cable by transmitting light down the glass-like core. Information is modulated on the light and conveyed between transmission points. The glass-like core has properties that can be measured and characterized.
When a fiber-optic cable is initially deployed, the cable must be tested and properly documented. As a result, if a fault occurs in the cable, a technician can properly troubleshoot the cable. For example, a fiber-optic cable may be damaged or disturbed by a backhoe or other excavation device. In addition, fiber-optic cables deployed for commercial use may have faults. For example, the glass-like core may crack or fracture under stress or when new pieces of fiber-optic cable are connected together (i.e., spliced), the two pieces of fiber-optic cable may not be properly spliced and light traveling down the glass-like core may be inappropriately reflected.
In modern networks, technicians use an Optical Time Domain Reflectometer (OTDR) to troubleshoot a fiber-optic cable. Initial test are made of the fiber-optic cable to properly calibrate the OTDR. The initial tests generate reference data that is used later to operate and locate the fiber-optic cable. An OTDR generates an initial light signal (e.g., reference trace) to characterize the fiber-optic cable. If the light encounters any discontinuities (e.g., faults), such as cracks, fractures, bends, breaks in the cable, connection points to other cables, or connections to end electronics, the initial light signal reflects back (e.g., reflected signal) to the OTDR. The OTDR calculates the distance to the discontinuity in the fiber by measuring the time elapsed between transmission of the initial light signal and reception of the reflection.
During operation of an OTDR, the OTDR is connected to the fiber-optic cable. The OTDR generates a reference trace to characterize the fiber (i.e., calibrate the OTDR). In addition, the OTDR generates a test trace to test the fiber. The reference trace is compared with the test trace. An operator inputs and maintains threshold information and known fault information. For example, the threshold information defines the amount of difference that the operator is willing to accept between a reference trace and a test trace before he considers a discontinuity a fault. Known faults are points along a cable run where the operator expects to see a discontinuity, such as a location where the fiber-optic cable is connected to other fiber-optic cables or equipment.
When new cable is deployed and the initial drawings are developed, initial readings are taken of the fiber-optic cable to identify the integrity of the cable and to physically locate the cable. For example, a fiber-optic cable may be terminated at one end so that test may be taken to calibrate the OTDR and also to identify the optical distance between the OTDR and the termination point. The reference data is used for any later readings and is also used to document the optical distance of the fiber on drawings, etc. The optical distance to various locations on the fiber-optic cable are often documented using marker numbers on the reference drawings.
In addition, when new equipment is attached to a fiber-optic cable, a new reference trace must be produced and new reference markers must be established. Therefore, there is a continual need to change and store new reference traces and update reference markers. For example, the continual development, redesign, and/or reengineering of a network results in continual changes and updates.
Reference drawings that have marker numbers along the path of the fiber-optic cable provide an optical distance. However, the reference drawings do not necessarily provide an accurate geographical distance. Sometimes the fiber-optic cable is coiled around an obstacle, such as a manhole cover, etc. As a result, during fault locating of a failed fiber-optic cable, it is very difficult to identify geographic locations based on the optical reading from the OTDR because the OTDR provides fault location data based on the optical distance. The technician must then relate the optical distance to a geographic location on a cable map.
Since the OTDR provides the optical distance along a fiber-optic path, when it is time to find a cable, it is difficult for a technician to locate the fiber-optic cable. As a result, in one conventional method, the technician has to physically go to the fiber-optic cable and create a disturbance in the cable. It should be appreciated that a similar procedure may be used when calibrating the fiber-optic cable and determining initial optical distances for documenting a cable map. The disturbance is then used to take the initial optical measurements of the fiber-optic cable or to geographically locate the fiber-optic cable.
To create a disturbance in the fiber-optic cable, the technician will cut the cable, place a terminating device on the cable, and then make the required measurements for fault isolation and/or cable documentation. In addition, if this is for initial testing of the fiber, reference data is collected. Once the location of the cable has been documented and/or the reference data has been collected, the cable must be reconnected through a cable splice. This process takes time to perform and in addition, if the cable is not properly spliced, more problems may be introduced.
Thus, a better system of calibrating and documenting a fiber-optic cable is required.